The present invention relates to a semiconductor memory apparatus, and more particularly, to a non-volatile memory of MoNoS construction.
The semiconductor memory apparatus of this type has a tunnel oxidizing film on a silicon substrate, an electric charge trap film on the tunnel oxidizing film, and a gate electrode on the trap film. The charge is trapped on the trap film from the channel portion by the application of a voltage to the gate electrode so as to remove the voltage from the gate. Thereafter, the channel is retained with the channel being retained in an ON or OFF condition by an electric field from the trapped electric charge. A nitride film or a mixed film is conventionally used as a trap film, with a defect in that the writing and erasing voltages must be high, because a high voltage is applied to the trap film.
An oxidizing film is provided on the trap film so that the size of the film may made thinner and so that the erasing and writing operations can be effected with low voltage. The oxidizing film prevents the flow of positive holes from the electrode and the penetration of electrons into the electrode, with a defect in that the writing and erasing voltages become higher as a high voltage is applied to the oxidizing film.